Transabdominal real-time ultrasonography was used to investigate antroduodenal motility effects of the prostaglandin E2 analogue enprostil. Ten healthy subjects were studied on two separate days, once after oral administration of one capsule of enprostil 35 micrograms 1 hour before the ingestion of 500 mL of meat soup and once without drug administration before the meal. The ultrasound probe was positioned at the level of the transpyloric plane to visualize the antrum, pylorus, and proximal duodenum simultaneously and thereafter vertically to visualize the antrum, superior mesenteric vein, and aorta simultaneously. The motility was videotaped for 15 minutes. The antroduodenal coordination, frequency and amplitude of antral contractions, and size of antral area were reduced, whereas the time during which the pylorus was wide open (greater than 5 mm) was increased after enprostil. It is concluded that antroduodenal motility can easily be visualized by ultrasonography. Therapeutic doses of enprostil impair antroduodenal peristalsis and coordination and open the pylorus in healthy subjects.